Injectable biomaterials for incontinence and vesico-ureteral reflux: Current status and future promise Tsai, C. C., V. Lin, et al. (2005), J Biomed Mater Res B Appl BiomaterAbstract: Many injectable biomaterials have been produced as bulking agents for compression of urethral sphincter or ureteral orifice for treating adult stress incontinence or vesico-ureteral reflux in pediatrics. The agents being developed include glutaraldehyde crosslinked collagen, dextranomer/hyaluronic acid copolymer, pyrolytic carbon-coated zirconium oxide beads, polydimethyl-siloxane microparticles, polytetrafluoroethylene paste, autologous fats, autologous chondrocytes, and others. Though less invasive nature of these agents has gained their popularity as a quick solution of the disease symptoms, most of such treatments fail to produce good long-term efficacy. The failure is likely caused by the rapid degradation of material implants and the lack of tissue regeneration/integration properties. We thus believe that a good injectable biomaterial for incontinence should possess the following two properties: (1) to resist degradation and to reside in the implantation sites for a long period of time or (2) to enhance tissue regeneration and to establish permanent periurethral or subureteric tissue. Here we report some recent results for supporting this hypothesis. (c) 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2005.

Injectable bulking agents for treating faecal incontinence Vaizey, C. J. and M. A. Kamm (2005), Br J Surg 92(5): 521-7.Abstract: BACKGROUND: Reports of the use of injectable bulking agents for faecal incontinence are currently confined to a small number of pilot studies. However, the use of these agents is rapidly becoming widespread based on this limited knowledge. METHODS: This review provides an overview of the products available and the methods of delivery based on the pilot studies, selected articles reporting experience of these agents in urology, plastic surgery and laryngology, and some animal studies. RESULTS AND CONCLUSIONS: Although bulking agents have been used to treat urinary incontinence for over four decades, their use in faecal incontinence has so far been limited. The large choice of products now available and the lack of a defined injection strategy will hamper efforts to produce meaningful prospective randomized trials.

Injectable gels of anionic collagen: rhamsan composites for plastic correction: preparation, characterization, and rheological properties de Paula, M., G. Goissis, et al. (2005), J Biomed Mater Res B Appl Biomater 75(2): 393-9.Abstract: The present article describes the preparation and characterization of anionic collagen gels obtained from porcine intestinal submucosa after 72 h of alkaline treatment and in the form of rhamsan composites to develop injectable biomaterials for plastic reconstruction. All materials were characterized by SDS/polyacrylamide gel electrophoresis, infrared spectroscopy, thermal stability, potentiometric titration, rheological properties, and fluidity tests. Biocompatibility was appraised after the injection of anionic collagen: rhamsan composites at 2.5% in 60 North Folk rabbits. Independently of processing, the collagen's secondary structure was preserved in all cases, and after 72 h of hydrolysis the collagen was characterized by a carboxyl group content of 346+/-9, which, at physiological pH, corresponds to an increase of 106+/-17 negative charges, in comparison to native collagen, due to the selective hydrolysis of asparagine and glutamine carboxyamide side chain. Rheological studies of composites at pH 7.4 in concentrations of 2, 4, and 6% (in proportions of 75:1 and 50:1) showed a viscoelastic behavior dependent on the frequency, which is independent of concentration and proportion. In both, the concentration of the storage modulus always predominated over the loss modulus (G'>G'' and delta<45 degrees). The results from creep experiments confirmed this behavior and showed that anionic collagen:rhamsan composites at pH 7.4 in the proportion of 50:1 are less elastic and more susceptible to deformation in comparison to gels in the proportion of 75:1, independent of concentration. This was further confirmed by flow experiments, indicating that the necessary force for the extrusion of anionic collagen:rhamsan composites, in comparison to anionic collagen, was significantly smaller and with a smooth flow. Biocompatibility studies showed that the tissue reaction of anionic collagen:rhamsan composites at 2.5% in the proportion of 75:1 was compatible with the application of these gels in plastic reconstruction. These results suggest that the association of collagen with rhamsan may be a good alternative in the replacement of glutaraldehyde to stabilize the microfibril assembly of commercial collagen gel preparations.

Injectable glycosaminoglycan hydrogels for controlled release of human basic fibroblast growth factor Cai, S., Y. Liu, et al. (2005), Biomaterials 26(30): 6054-67.Abstract: Synthetic hydrogel mimics of the extracellular matrix (ECM) were created by crosslinking a thiol-modified analog of heparin with thiol-modified hyaluronan (HA) or chondroitin sulfate (CS) with poly(ethylene glycol) diacrylate (PEGDA). The covalently bound heparin provided a crosslinkable analog of a heparan sulfate proteoglycan, thus providing a multivalent biomaterial capable of controlled release of basic fibroblast growth factor (bFGF). Hydrogels contained >97% water and formed rapidly in <10min. With as little as 1% (w/w) covalently bound heparin (relative to total glycosaminoglycan content), the rate of release of bFGF in vitro was substantially reduced. Total bFGF released increased with lower percentages of heparin; essentially quantitative release of bFGF was observed from heparin-free hydrogels. Moreover, the hydrogel-released bFGF retained 55% of its biological activity for up to 28 days as determined by a cell proliferation assay. Finally, when these hydrogels were implanted into subcutaneous pockets in Balb/c mice, neovascularization increased dramatically with HA and CS hydrogels that contained both bFGF and crosslinked heparin. In contrast, hydrogels lacking bFGF or crosslinked heparin showed little increase in neovascularization. Thus, covalently linked, heparin-containing glycosaminoglycan hydrogels that can be injected and crosslinked in situ constitute highly promising new materials for controlled release of heparin-binding growth factors in vivo.

Injectable silicone biomaterial for faecal incontinence due to internal anal sphincter dysfunction Kenefick, N. J., C. J. Vaizey, et al. (2002), Gut 51(2): 225-8.Abstract: BACKGROUND: A weak or disrupted internal anal sphincter can cause passive faecal incontinence. Conservative measures may help some patients but there is no simple surgical solution for those who fail conservative treatment. A successful technique using trans-sphincteric injection of a bulking agent to augment the internal anal sphincter was developed in a previous pilot study. AIM: To determine the clinical results and underlying physiological effects of biomaterial injection. PATIENTS: Six patients (four males, median age 53 years (range 36-65)) with faecal incontinence to solid or liquid stool related to poor internal anal sphincter function, of varied aetiology, were recruited. METHODS: Silicone based biomaterial injections were performed, under local anaesthesia, with antibiotic cover. Three injections were placed circumferentially, trans-sphincterically, entering away from the anal margin and injecting at or just above the dentate line. Anorectal physiological studies, endoanal ultrasound, a bowel symptom diary, a validated incontinence score, and quality of life questionnaires were completed before treatment and on completion of follow up. RESULTS: At a median follow up of 18 months (range 15-19), five of six patients had marked symptom improvement. Faecal incontinence scores improved from a median of 14/24 (range 11-20) before to 8/24 (6-15) after injection. Short form-36 quality of life physical and social function scores improved from a median of 26/100 (5-33) to 79/100 (25-100) and from 10/100 (5-37) to 100/100 (50-100), respectively. There was a corresponding physiological increase in maximum anal resting and squeeze pressures. Ultrasound showed the Bioplastique to be retained in the correct position in the improved patients without migration. There were no complications. CONCLUSION: Trans-sphincteric injection of silicone biomaterial can provide a marked improvement in faecal incontinence related to a weak or disrupted internal anal sphincter. This is associated with improved sphincter function and quality of life.

Injectable silicone biomaterial for fecal incontinence caused by internal anal sphincter dysfunction is effective Tjandra, J. J., J. F. Lim, et al. (2004), Dis Colon Rectum 47(12): 2138-46.Abstract: PURPOSE: Fecal incontinence caused by a weak or disrupted internal anal sphincter is common but there has been no effective treatment. This prospective study evaluates the medium-term clinical effects of an injectable silicone biomaterial, PTP (Bioplastique), used to augment the internal anal sphincter. METHOD: Eighty-two patients (64 females; median age, 66 years) with severe fecal incontinence and a low anal resting pressure caused by internal anal sphincter dysfunction (defect, n = 11; intact, n = 71) were randomized to PTP injection into intersphincteric space and internal anal sphincter with (Group A, n = 42) or without (Group B, n = 40) guidance by endoanal ultrasound. Both groups were similar in terms of age, gender, past anorectal surgery, duration of follow-up (median, 6 months; range, 1-12 months), and baseline continence score. Sixty-two percent of Group A and 55 percent of Group B had prolonged pudendal nerve terminal motor latency. RESULTS: There was no significant complication. Two patients in Group A and four patients in Group B noted minor discomfort at injection sites. At one month postprocedure, endoanal ultrasound confirmed retention of silicone biomaterial without migration. In both groups, fecal continence was significantly improved by PTP implants 1 month after injection, but continued to improve significantly for up to 12 months in Group A and 6 months in Group B (P < 0.001). Improvement in fecal continence and maximum anal resting pressure was significantly greater in Group A, in whom injection was guided by endoanal ultrasound, than in Group B. At three months after injection, significantly more Group A patients than Group B patients achieved >50 percent improvement in Wexner's continence score (69 percent vs. 40 percent; P = 0.014). Ninety-three percent of Group A and 92 percent of Group B had >50 percent improvement in global quality of life scores (visual analog scale). At a median follow-up of 6 months, all domains of the fecal incontinence quality of life scale improved significantly in both groups; however, the physical function and mental health scores of Short Form-12 only improved in Group A. A prolonged pudendal nerve terminal motor latency had no effect on functional outcome in either group. CONCLUSION: Injection of silicone biomaterial provided a marked improvement in fecal continence and quality of life in patients with internal sphincter dysfunction, despite the presence of pudendal neuropathy.

Injectable skin fillers Narins, R. S. and P. H. Bowman (2005), Clin Plast Surg 32(2): 151-62.Abstract: The list of injectable skin fillers available for soft tissue augmentation is constantly growing, giving aesthetic surgeons more options in the treatment of scars, lines, and wrinkles. Each type of filler is distinct with regard to intended use, placement technique, duration in tissue, ease of use, and cost. Physicians who are well acquainted with the strengths and weaknesses of each class of filler will be best equipped to use this rapidly expanding class of agents in serving their patients. The authors review the most commonly used injectable skin fillers and discuss their differences in terms of composition, source (eg, human, animal), intended use, placement technique, tissue duration (nonpermanent, semipermanent, or permanent), side effects, and specific advantages and disadvantages.

Injected hyaluronidase reduces restylane-mediated cutaneous augmentation Vartanian, A. J., A. S. Frankel, et al. (2005), Arch Facial Plast Surg 7(4): 231-7.Abstract: OBJECTIVE: To determine the effects of injected hyaluronidase in cutaneous areas previously augmented with Restylane (Q-Med AB, Uppsala, Sweden), a nonanimal, stabilized hyaluronic acid (NASHA) gel. METHODS: A prospective, randomized study was undertaken in 2 parts. First, the effects of hyaluronidase and saline were compared on post-NASHA dermal augmentation. Next, 3 different doses of hyaluronidase were evaluated after NASHA gel dermal augmentation. A blinded evaluator assigned postinjection skin scores. Each patient served as his or her own control. RESULTS: Hyaluronidase dramatically reduced the size of the augmentation created by injected Restylane in all of our subjects. A comparison of average scores of saline-injected sites vs hyaluronidase-injected sites revealed a statistically significant difference. By 4 to 7 days after hyaluronidase injection, skin scores were at 20% of baseline (P

Injection therapy for stress urinary incontinence in adult women ter Meulen, H. and E. van Kerrebroeck (2004), Expert Rev Med Devices 1(2): 205-13.Abstract: Stress urinary incontinence (SUI) is prevalent in adult women and has a considerable impact on quality of life. However, it often remains undiagnosed and therefore untreated. Noninvasive treatment is likely to be offered in mild cases and may entail pelvic floor muscle re-education, minimally invasive devices or pharmacotherapy. Surgical intervention is widely considered as the only effective option for more severe SUI, although it is not suitable for all patients. Injection therapy with urethral bulking agents represents an alternative minimally invasive procedure and can be used for all types of SUI. Many bulking agents have been developed, although the ideal remains to be discovered. The safety and durability of agents remain a concern. No differences in agents from an efficacy point of view have been found. For many years urethral injection could only be administered endoscopically. The recent development of devices for blind injection has increased the speed and convenience of urethral injection, removing the need for surgical facilities. The subjective cure rate after injection therapy is higher than the objective one. A focus on the patient's wishes and expectations with respect to success and risks of a treatment for SUI is required. In addition, randomized clinical trials are mandatory to establish the place and efficacy of urethral bulking agents compared with conservative therapy (pelvic floor muscle re-education) in treating SUI in adult women.

Inosculation of tissue-engineered capillaries with the host's vasculature in a reconstructed skin transplanted on mice Tremblay, P. L., V. Hudon, et al. (2005), Am J Transplant 5(5): 1002-10.Abstract: The major limitation for the application of an autologous in vitro tissue-engineered reconstructed skin (RS) for the treatment of burnt patients is the delayed vascularization of its relatively thick dermal avascular component, which may lead to graft necrosis. We have developed a human endothelialized reconstructed skin (ERS), combining keratinocytes, fibroblasts and endothelial cells (EC) in a collagen sponge. This skin substitute then spontaneously forms a network of capillary-like structures (CLS) in vitro. After transplantation to nude mice, we demonstrated that CLS containing mouse blood were observed underneath the epidermis in the ERS in less than 4 days, a delay comparable to our human skin control. In comparison, a 14-day period was necessary to achieve a similar result with the non-endothelialized RS. Furthermore, no mouse blood vessels were ever observed close to the epidermis before 14 days in the ERS and the RS. We thus concluded that the early vascularization observed in the ERS was most probably the result of inosculation of the CLS network with the host's capillaries, rather than neovascularization, which is a slower process. These results open exciting possibilities for the clinical application of many other tissue-engineered organs requiring a rapid vascularization.

Insecticidal and fungicidal activity of new synthesized chitosan derivatives Rabea, E. I., M. E. Badawy, et al. (2005), Pest Manag Sci 61(10): 951-60.Abstract: Chitosan, the N-deacetylated derivative of chitin, is a potential biopolysaccharide owing to its specific structure and properties. In this paper, we report on the synthesis of 24 new chitosan derivatives, N-alkyl chitosans (NAC) and N-benzyl chitosans (NBC), that are soluble in dilute aqueous acetic acid. The different derivatives were synthesized by reductive amination and analyzed by 1H NMR spectroscopy. A high degree of substitution (DS) was obtained with N-(butyl)chitosan (DS 0.36) at a 1:1 mole ratio for NAC derivatives and N-(2,4-dichlorobenzyl)chitosan (DS 0.52) for NBC derivatives. Their insecticidal and fungicidal activities were tested against larvae of the cotton leafworm Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae), the grey mould Botrytis cinerea Pers (Leotiales: Sclerotiniaceae) and the rice leaf blast Pyricularia grisea Cavara (Teleomorph: Magnaporthe grisea (Hebert) Barr). The oral feeding bioassay indicated that all the derivatives had significant insecticidal activity at 5 g kg(-1) in artificial diet. The most active was N-(2-chloro-6-fluorobenzyl)chitosan, which caused 100% mortality at 0.625 g kg(-1), with an estimated LC50 of 0.32 g kg(-1). Treated larvae ceased feeding after 2-3 days; the mechanism of action remains unknown. In a radial hyphal growth bioassay with both plant pathogens, all derivatives showed a higher fungicidal action than chitosan. N-Dodecylchitosan, N-(p-isopropylbenzyl)chitosan and N-(2,6-dichlorobenzyl)chitosan were the most active against B cinerea, with EC50 values of 0.57, 0.57 and 0.52 g litre(-1), respectively. Against P grisea, N-(m-nitrobenzyl)chitosan was the most active, with 77% inhibition at 5 g litre(-1). The effect of different substitutions is discussed in relation to insecticidal and fungicidal activity.

In-situ deposition of Pd nanoparticles on tubular halloysite template for initiation of metallization Fu, Y., L. Zhang, et al. (2005), J Nanosci Nanotechnol 5(4): 558-64.Abstract: Halloysite template has a tubular microstructure; its wall has a multi-layer aluminosilicate structure. A new catalytic method is adopted here, through the in-situ reduction of Pd ions on the surface of tubular halloysite by methanol to initiate electroless plating; the detailed deposition features of Pd nanoparticles are investigated for the first time. The results indicate that an in-situ reduction and deposition of Pd occurs at room temperature, in which the halloysite template plays an important role. Impurities in halloysite (such as ferric oxide) influence the formation and distribution of the Pd nanoparticles. The Pd nanoparticles are of a non-spherical shape in most cases, which would be caused by the irregular appearance of halloysite. No intercalation of the nanoparticles occurs between the aluminosilicate layers in the halloysite. The diameter of Pd nanoparticles increases with time; the average diameter ranges from 1 nm to 4 nm. Pd nanoparticles on a halloysite template can catalyze electroless deposition of Ni to prepare a novel nano-sized cermet at low cost. This practicable catalytic method could also be used on other clay substrates for the initiation of metallization.

In-situ preparation of poly(propylene fumarate)--hydroxyapatite composite Hakimimehr, D., D. M. Liu, et al. (2005), Biomaterials 26(35): 7297-303.Abstract: In-situ precipitation of hydroxyapatite (HAp) in the presence of poly(propylene fumarate) (PPF) is investigated. Amorphous calcium phosphate (ACP) precipitates in the presence of the polymer and remains in the amorphous form for a relatively long time, e.g. even after 24 h of coexistence with the mother solution. Our observations suggest that PPF interacts with the surface of the ACP particles and prevents them from transformation to crystalline hydroxyapatite. The PPF polymer seems to be more efficient in hindering the ACP to HAp transformation at higher pH conditions. From spectroscopic observations we hypothesize that the C=O bond of the PPF molecules interact with the calcium ion of the ACP particles. In case of low molecular weight PPF this interaction may lead to the incorporation of the polymer within the growing ACP particles.

In-situ synthesis and performance of titanium oxide/poly(methyl methacrylate) nanocomposites Bandugula, U. C., L. M. Clayton, et al. (2005), J Nanosci Nanotechnol 5(5): 814-9.Abstract: Polymer nanocomposites have elicited extensive research efforts due to their potential to exhibit spectacular properties. They have immense potential and are befitting materials to serve as an ideal and futuristic alternative for varied applications. Poly(methyl methacrylate) (PMMA) and titanium oxide (TiO2) nanocomposites used in this study were fabricated by an in-situ free radical polymerization process. Three point bend tests were conducted with a modified universal microtribometer to evaluate fracture toughness. The results indicated that the stress intensity values increase as the concentration of titanium oxide increases up to 1 vol% and subsequently decrease at higher concentrations. Scanning electron microscopy (SEM) images of fracture surfaces afforded clues as to the possible deformation mechanism. Ultraviolet-visible spectroscopy (UV-vis) evaluated the degree of transparency of the nanocomposites. It was observed that samples became opaque as the concentration was increased beyond 0.01% volume fraction. X-ray diffraction characterized the TiO2 crystalline phase and Scherrer's equation was used to calculate the crystallite size. Among the concentrations considered the 3% volume fraction sample had the largest crystallite size. Finally, microhardness measurements further characterized the mechanical properties of the composites.

Insulator semiconductor structures coated with biodegradable latexes as encapsulation matrix for urease Barhoumi, H., A. Maaref, et al. (2005), Biosens Bioelectron 20(11): 2318-23.Abstract: A new urea biosensor for clinical applications was obtained by immobilization of urease within different latex polymers functionalized by hydroxy, acetate and lactobionate groups. Responses of these biosensors based on pH-ion-selective field effect insulator-semiconductor (IS) systems to urea additions were evaluated by capacitance measurements. UV-visible spectroscopy was used to check the urease activity in various matrixes. A good retention of the catalytic urease activity in the case of the cationic polymers was observed. In addition, rotating disk electrode experiments were carried out to determine the matrix permeability characteristics. Under optimal conditions, i.e. buffer capacity corresponding to 5 mM phosphate buffer, the urea enzyme insulator semiconductor (ENIS) sensors showed a linear response for urea concentrations in the range 10(-1.5) to 10(-4)M. Furthermore, kinetic parameters for the immobilized urease were obtained from Lineweaver-Burk plot. Clearly, a fast response and a good adhesion for the urease-acetate polymer composite films, prepared without using glutaraldehyde as cross-linking agent was observed.

Insulin-like growth factor I-releasing alginate-tricalciumphosphate composites for bone regeneration Luginbuehl, V., E. Wenk, et al. (2005), Pharm Res 22(6): 940-50.Abstract: PURPOSE: Development and characterization of an in situ-forming, osteoconductive, and growth factor-releasing bone implant. METHODS: Injectable in situ-forming scaffolds were prepared from a 2% (m/v) alginate solution, tricalciumphosphate (TCP) granules, and poly(lactide-co-glycolide) microspheres (MS), loaded with the osteoinductive growth factor insulin-like growth factor I (IGF-I). Scaffolds were prepared by mixing the components followed by hydrogel formation through calcium carbonate-induced physical cross-linking of the alginate at slightly acidic pH. Physical-chemical properties and cell biocompatibility using osteoblast-like cells (MG-63 and Saos-2) of these scaffolds were investigated. RESULTS: The addition of TCP to the alginate resulted in reduced swelling and gelation time and an increase in stiffness. Osteoblast-like cells (MG-63 and Saos-2) did not show toxic reactions and adhered circumferentially to the TCP granules surface. The addition of the IGF-I MS resulted in an up to sevenfold increased proliferation rate of MG-63 cells as compared to scaffold preparations without IGF-I MS. The alkaline phosphate (ALP) activity-a parameter for osteblastic activity-increased with increasing amounts of TCP in Saos-2 loaded composite scaffolds. CONCLUSIONS: A prototype in situ-hardening composite system for conformal filling of bone defects supporting osteoblastic activity for further clinical testing in relevant fracture models was developed and characterized.

Insulinoma cell line (MIN6) adhesion and spreading mediated by Arg-Gly-Asp (RGD) sequence conjugated in thermo-reversible gel Park, K. H., K. Na, et al. (2005), J Biosci Bioeng 99(6): 598-602.Abstract: We have functionalized gels with a putative cell-binding (-Arg-Gly-Asp-) (RGD) domain in an effort to regulate mammalian cell behavior in cells entrapped with gel. Adhesion molecules composed of Gly-Arg-Gly-Asp-Ser (GRGDS) peptides and cell recognition ligands were inculcated into thermo-reversible hydrogel composed of N-isopropylacrylamide, with a small amount of succinyl poly(ethylene glycol) (PEG) acrylate (MW 2000) used as a biomimetic extracellular matrix (ECM). The GRGDS-containing p(NiPAAm-co-PEG) copolymer gel was studied in vitro for its ability to promote cell spreading and to increase the viability of cells by introducing PEG spacers. Hydrogel lacking the adhesion molecules proved to be a poor ECM for adhesion, permitting only a 20% spread of the seeded cells after 10 d. When PEG spacer arms, immobilized by a peptide linkage, had been integrated into the hydrogel, conjugation of RGD promoted cell spread by 300% in a 28-d trial. In addition, in a serum-free medium, only GRGDS peptides conjugated with the spacer arm were able to promote cell spread.

Integrating dental anatomy and biomaterials: an innovative use of composite resin Allen, K. L. and M. McAndrew (2004), Gen Dent 52(2): 132-3.Abstract: As part of the new integrated curriculum at the New York University College of Dentistry, a pilot program uses composite resins to teach dental anatomy. The Department of Biomaterials and Biomimetics, in conjunction with the Department of Cariology and Operative Dentistry, has created a teaching module to replicate the morphology of a central incisor through the manipulation and placement of a composite resin.

Integration of biomaterials implanted into abdominal wall: process of scar formation and macrophage response Bellon, J. M., J. Bujan, et al. (1995), Biomaterials 16(5): 381-7.Abstract: The behaviour of two biomaterials polytetrafluoroethylene (PTFE) and polypropylene (PL) has been studied, focussing especially on the macrophage response to the implant, as well as on certain aspects of the process of scar formation. A total of 24 animals (white New Zealand rabbits) received prostheses implanted into the anterior abdominal wall in such a way as to involve every layer over an area of 7 cm x 5 cm. The interfaces formed with the visceral peritoneum, subcutaneous tissue layer and the recipient muscle-aponeurotic tissue were assessed. The techniques employed were light microscopy, scanning electron microscopy and immunohistochemical methods, the latter using a monoclonal antibody specific for rabbit macrophages (RAM-11). From the results obtained, it can be seen that: (a) the structure of PL allows its total integration with the reparative tissue, while PTFE becomes encapsulated, on both the subcutaneous and the peritoneal aspects, by orderly connective tissue; (b) the macrophage response, determined on the basis of the presence of labelled macrophages, shows a similar pattern in both biomaterials; and (c) angiogenesis is very intense in the PL mesh, whereas the PTFE prosthesis undergoes almost no vascular colonization.